Evaluation of the J2000 groundwater component

Loire Catchment

Author

R. C. Kubina

Published

16-04-2024

1 Decision for z-score normalization

Since the z-score normalization is used for the evaluation of the Explore2 project, it makes sense to use it here as well for reasons of comparability. To unify it the data was monthly aggregated before the normalization. The normalized value is called Standardized Piezometric Level Index (SPLI) in the Explore2 report, which nomenclature will be used from now on. Also the begin of the comparison was set to the year 2004, so there is the most data for all stations available and the simulation time is reduced.

Figure 1: Time series of SPLI

For the aggregation to average monthly values, hydrological years with less than 90% data availability were removed.

Figure 2: Regime of hydrological year
Figure 3: Duration curves
Figure 4: NSE(SPLI) of J2K output to ADES

2 Limitations due to the calibration

If you take a look at the plots, two unwanted patterns are recognizable:

  • High frequency in time series, resulting in 95th-Percentile = maximum in duration curves \(\rightarrow\) RG1_max is too small
  • No variation in time series and values around zero (the mean), resulting in IQR = 0 \(\rightarrow\) RG1_k is too big

These two criteria give the possibility to evaluate/improve the groundwater component of HRUs with no piezometers in them.

3 Evaluation criteria

For further analysis and the calibration of the model to improve the representation of the groundwater component multiple goodness-of-fit tests will be used. Since the main purpose of the model is to simulate the discharge in the Loire catchment, the Kling-Gupta efficiency (KGE) of the square root of the discharge, will be the criterion (also used in Explore2 for J2K model). For the groundwater component two different types of criteria will be used:

  • if there are reference piezometers: the Nash-Sutcliffe efficiency of the SPLI, Correlation, time lag of maximum/minimum of the regime
  • if there are no reference piezometers: difference of 95th-Percentile to maximum and IQR

4 Identifying range of RG1_max and RG1_k for calibration

Table 1: Cailbration parameters to identify calibration range
Run RG1_max RG1_k
1 10 10
2 10 30
3 10 180
4 10 360
5 10 500
6 50 10
7 50 30
8 50 180
9 50 360
10 50 500
11 100 10
12 100 30
13 100 180
14 100 360
15 100 500
16 500 10
17 500 30
18 500 180
19 500 360
20 500 500
21 1000 10
22 1000 30
23 1000 180
24 1000 360
25 1000 500
Figure 5: IQR and difference between maximum and 95th-percentile (max_perc) for each hgeoID